“We are launching this clemency initiative in order to quickly and effectively identify appropriate candidates, candidates who have a clean prison record, do not present a threat to public safety, and were sentenced under out-of-date laws that have since been changed, and are no longer seen as appropriate,” Deputy Attorney General James Cole said at a news conference.

Cole said the main thrust of the effort will be to shorten sentences of inmates whose long prison terms were due in part to the disparity between the treatment of powdered cocaine and crack cocaine in federal law. Obama signed legislation in 2010 to reduce that disparity, which many critics complained unfairly affected minority offenders.

“While those sentenced prior to the Fair Sentencing Act may be the most obvious candidates, this initiative is not limited to crack offenders,” Cole declared.

The Justice Department said the new clemency initiative will be open to prisoners meeting six criteria: “They must be (1) inmates who are currently serving a federal sentence in prison and, by operation of law, likely would have received a substantially lower sentence if convicted of the same offense today; (2) are non-violent, low-level offenders without significant ties to large-scale criminal organizations, gangs, or cartels; (3) have served at least 10 years of their sentence; (4) do not have a significant criminal history; (5) have demonstrated good conduct in prison; and (6) have no history of violence prior to or during their current term of imprisonment.”

Asked if the department was bracing for the possibility that those who are released early may commit additional crimes, Cole noted that people are let out of prison all the time after completing their sentences, so those receiving commutations are not in much of a different position.

"What we're going to say is they need to be dealt with as any other person who commits a serious crime," Cole said. "We have thousands of people coming out of our prison system every day. … We do our best to make sure the re-entry process for those people puts them in a situation where they can re-enter society successfully."

The move drew criticism from House Judiciary Committee Chairman Bob Goodlatte (R-Va.), who argued it was just the latest in a series of Obama administration that have not shown proper respect for the law.

"In an unprecedented move to dramatically expand the clemency process for federal drug offenders, President Obama has again demonstrated his blatant disregard for our nation’s laws and our system of checks and balances embedded in the U.S. Constitution," Goodlatte said in a statement. “Congress is charged with establishing categories of punishments for federal crimes, not the president. This pattern of President Obama picking and choosing which laws to enforce and which to change according to his whim is an alarming trend that must stop."

While the clemency move could be seen as in tension with the law or in defiance of Congress's electing not to make certain reforms retroactive, the Constitution gives the president unfettered discretion to grand pardons, commutations and other forms of clemency to anyone he wishes for any reason at all or for no reason whatsoever.

Responding to Goodlatte on Twitter, White House spokesman Matt Lehrich pointed to a 2001 hearing in which the congressman called clemency "a very important power" and said it has been used "for the purpose of accomplishing justice or mercy as a last resort, where fairness simply has not taken hold in other aspects of our judicial process."

Cole said the program to seek clemency applications is not limited to drug offenders, but he didn't elaborate on who else might be eligible. "The reality is that the vast majority will probably be drug offenders. ... We’re not foreclosing the possibility there are other types of sentences that are worthy of this kind of clemency. We're open to looking at whatever comes in," he said.

A top sentencing law expert said crack cases are the only ones that clearly qualify under the criteria, but other drug convicts could argue that it is "likely" they would have gotten lower sentences today, particularly since the Supreme Court made sentencing guidelines advisory in 2005. The sentencing commission has also voted to lower guidelines somewhat for all drug offenses, but it's unclear whether those reductions would be substantial enough to meet the DOJ criteria.

"What's really challenging across a number of dimensions is there are by my lights no other drug offenses in which the law has indisputably made their sentences lower today" other than crack offenders, said Ohio State University law professor Doug Berman.

Berman said some white-collar criminals, such as those involved in fraud schemes, who could also argue that they were hit with sentencing-guidelines-driven prison terms longer than a judge would have applied today. "I am certain there are at least some white-collar criminals who got pretty sever sentences under the sentencing guideliness before Booker came along," he said, referring to the 2005 Supreme Court case. "Those folks have an awfully good basis, I would think, of saying I would likely have gotten a shorter sentence under the law today."

One outstanding question: whether any child pornography offenders might meet the criteria. Berman said that if some do, they would likely have been sentenced between 2003 (when Congress passed a measure barring judges from imposing below-guidelines sentences in such cases) and 2005 (when the Supreme Court made the guidelines advisory).

Berman said it will be interesting to see whether private lawyers organizing clemency submissions will take cases for white-collar offenders or those charged with child pornography crimes. "This is where things will get real dicey, not just on the Justice Department side but on the defense bar side," he said.

A Justice Department official who asked not to be named threw cold water on the notion that kiddie porn convicts might successfully navigate the clemency process. "While the initiative does not rule out any specific offense, I think we would have a hard time sending the president a petition for a child pornographer or those who distribute it," the official said.

However, the Justice Department did declare last year that the guidelines for such offenses were outdated and in need of changes because they "at times under-represent and at times over-represent the seriousness of an offender's conduct and the danger an offender possesses."

Cole also announced Wednesday the departure of the Justice Department official who has traditionally overseen the vetting of clemency applications, Pardon Attorney Ronald Rodgers. He was criticized in an inspector general's report for not forwarding important information to the White House and has been viewed by clemency advocates as an obstacle to getting applications to the president.

A department official said earlier that Rodgers was resigning, but Cole said he would be reassigned to another senior position in the department at his request.

The new pardon attorney will be Deborah Leff, who's currently a top adviser to Attorney General Eric Holder on access-to-justice issues. She's also a former ABC News producer.

UPDATE (Wednesday, 10:08 A.M): This post has been updated with news of Leff's appointment.

UPDATE 2 (Wednesday, 12:11 P.M.): This post has been updated with additional detail from Cole's press conference, as well as reaction from Berman and a Justice Department official.

UPDATE 3 (Wednesay, 5:05 P.M.): This post has been updated with comments from Goodlatte and Lehrich.